From cc4ce37bed85989daf8f38bf19ea591f3b36fb0c Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 31 Jan 2024 15:56:06 -0800 Subject: KVM: SVM: Set sev->asid in sev_asid_new() instead of overloading the return Explicitly set sev->asid in sev_asid_new() when a new ASID is successfully allocated, and return '0' to indicate success instead of overloading the return value to multiplex the ASID with error codes. There is exactly one caller of sev_asid_new(), and sev_asid_free() already consumes sev->asid, i.e. returning the ASID isn't necessary for flexibility, nor does it provide symmetry between related APIs. Reviewed-by: Tom Lendacky Link: https://lore.kernel.org/r/20240131235609.4161407-2-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'arch/x86/kvm/svm') diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index f760106c31f8..7c000088bca6 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -179,7 +179,8 @@ again: mutex_unlock(&sev_bitmap_lock); - return asid; + sev->asid = asid; + return 0; e_uncharge: sev_misc_cg_uncharge(sev); put_misc_cg(sev->misc_cg); @@ -246,7 +247,7 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle) static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) { struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; - int asid, ret; + int ret; if (kvm->created_vcpus) return -EINVAL; @@ -257,10 +258,9 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) sev->active = true; sev->es_active = argp->id == KVM_SEV_ES_INIT; - asid = sev_asid_new(sev); - if (asid < 0) + ret = sev_asid_new(sev); + if (ret) goto e_no_asid; - sev->asid = asid; ret = sev_platform_init(&argp->error); if (ret) -- cgit v1.2.3 From 466eec4a22a76c462781bf6d45cb02cbedf21a61 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 31 Jan 2024 15:56:07 -0800 Subject: KVM: SVM: Use unsigned integers when dealing with ASIDs Convert all local ASID variables and parameters throughout the SEV code from signed integers to unsigned integers. As ASIDs are fundamentally unsigned values, and the global min/max variables are appropriately unsigned integers, too. Functionally, this is a glorified nop as KVM guarantees min_sev_asid is non-zero, and no CPU supports -1u as the _only_ asid, i.e. the signed vs. unsigned goof won't cause problems in practice. Opportunistically use sev_get_asid() in sev_flush_encrypted_page() instead of open coding an equivalent. Reviewed-by: Tom Lendacky Link: https://lore.kernel.org/r/20240131235609.4161407-3-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'arch/x86/kvm/svm') diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 7c000088bca6..eeef43c795d8 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -84,9 +84,10 @@ struct enc_region { }; /* Called with the sev_bitmap_lock held, or on shutdown */ -static int sev_flush_asids(int min_asid, int max_asid) +static int sev_flush_asids(unsigned int min_asid, unsigned int max_asid) { - int ret, asid, error = 0; + int ret, error = 0; + unsigned int asid; /* Check if there are any ASIDs to reclaim before performing a flush */ asid = find_next_bit(sev_reclaim_asid_bitmap, nr_asids, min_asid); @@ -116,7 +117,7 @@ static inline bool is_mirroring_enc_context(struct kvm *kvm) } /* Must be called with the sev_bitmap_lock held */ -static bool __sev_recycle_asids(int min_asid, int max_asid) +static bool __sev_recycle_asids(unsigned int min_asid, unsigned int max_asid) { if (sev_flush_asids(min_asid, max_asid)) return false; @@ -143,8 +144,9 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev) static int sev_asid_new(struct kvm_sev_info *sev) { - int asid, min_asid, max_asid, ret; + unsigned int asid, min_asid, max_asid; bool retry = true; + int ret; WARN_ON(sev->misc_cg); sev->misc_cg = get_current_misc_cg(); @@ -188,7 +190,7 @@ e_uncharge: return ret; } -static int sev_get_asid(struct kvm *kvm) +static unsigned int sev_get_asid(struct kvm *kvm) { struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; @@ -284,8 +286,8 @@ e_no_asid: static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error) { + unsigned int asid = sev_get_asid(kvm); struct sev_data_activate activate; - int asid = sev_get_asid(kvm); int ret; /* activate ASID on the given handle */ @@ -2312,7 +2314,7 @@ int sev_cpu_init(struct svm_cpu_data *sd) */ static void sev_flush_encrypted_page(struct kvm_vcpu *vcpu, void *va) { - int asid = to_kvm_svm(vcpu->kvm)->sev_info.asid; + unsigned int asid = sev_get_asid(vcpu->kvm); /* * Note! The address must be a kernel address, as regular page walk @@ -2630,7 +2632,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm) void pre_sev_run(struct vcpu_svm *svm, int cpu) { struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu); - int asid = sev_get_asid(svm->vcpu.kvm); + unsigned int asid = sev_get_asid(svm->vcpu.kvm); /* Assign the asid allocated with this SEV guest */ svm->asid = asid; -- cgit v1.2.3 From 0aa6b90ef9d75b4bd7b6d106d85f2a3437697f91 Mon Sep 17 00:00:00 2001 From: Ashish Kalra Date: Wed, 31 Jan 2024 15:56:08 -0800 Subject: KVM: SVM: Add support for allowing zero SEV ASIDs Some BIOSes allow the end user to set the minimum SEV ASID value (CPUID 0x8000001F_EDX) to be greater than the maximum number of encrypted guests, or maximum SEV ASID value (CPUID 0x8000001F_ECX) in order to dedicate all the SEV ASIDs to SEV-ES or SEV-SNP. The SEV support, as coded, does not handle the case where the minimum SEV ASID value can be greater than the maximum SEV ASID value. As a result, the following confusing message is issued: [ 30.715724] kvm_amd: SEV enabled (ASIDs 1007 - 1006) Fix the support to properly handle this case. Fixes: 916391a2d1dc ("KVM: SVM: Add support for SEV-ES capability in KVM") Suggested-by: Sean Christopherson Signed-off-by: Ashish Kalra Cc: stable@vger.kernel.org Acked-by: Tom Lendacky Link: https://lore.kernel.org/r/20240104190520.62510-1-Ashish.Kalra@amd.com Link: https://lore.kernel.org/r/20240131235609.4161407-4-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) (limited to 'arch/x86/kvm/svm') diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index eeef43c795d8..5f8312edee36 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -144,10 +144,21 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev) static int sev_asid_new(struct kvm_sev_info *sev) { - unsigned int asid, min_asid, max_asid; + /* + * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid. + * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1. + * Note: min ASID can end up larger than the max if basic SEV support is + * effectively disabled by disallowing use of ASIDs for SEV guests. + */ + unsigned int min_asid = sev->es_active ? 1 : min_sev_asid; + unsigned int max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid; + unsigned int asid; bool retry = true; int ret; + if (min_asid > max_asid) + return -ENOTTY; + WARN_ON(sev->misc_cg); sev->misc_cg = get_current_misc_cg(); ret = sev_misc_cg_try_charge(sev); @@ -159,12 +170,6 @@ static int sev_asid_new(struct kvm_sev_info *sev) mutex_lock(&sev_bitmap_lock); - /* - * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid. - * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1. - */ - min_asid = sev->es_active ? 1 : min_sev_asid; - max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid; again: asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid); if (asid > max_asid) { @@ -2234,8 +2239,10 @@ void __init sev_hardware_setup(void) goto out; } - sev_asid_count = max_sev_asid - min_sev_asid + 1; - WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)); + if (min_sev_asid <= max_sev_asid) { + sev_asid_count = max_sev_asid - min_sev_asid + 1; + WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)); + } sev_supported = true; /* SEV-ES support requested? */ @@ -2266,7 +2273,9 @@ void __init sev_hardware_setup(void) out: if (boot_cpu_has(X86_FEATURE_SEV)) pr_info("SEV %s (ASIDs %u - %u)\n", - sev_supported ? "enabled" : "disabled", + sev_supported ? min_sev_asid <= max_sev_asid ? "enabled" : + "unusable" : + "disabled", min_sev_asid, max_sev_asid); if (boot_cpu_has(X86_FEATURE_SEV_ES)) pr_info("SEV-ES %s (ASIDs %u - %u)\n", -- cgit v1.2.3 From fdd58834d132046149699b88a27a0db26829f4fb Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 31 Jan 2024 15:56:09 -0800 Subject: KVM: SVM: Return -EINVAL instead of -EBUSY on attempt to re-init SEV/SEV-ES Return -EINVAL instead of -EBUSY if userspace attempts KVM_SEV{,ES}_INIT on a VM that already has SEV active. Returning -EBUSY is nonsencial as it's impossible to deactivate SEV without destroying the VM, i.e. the VM isn't "busy" in any sane sense of the word, and the odds of any userspace wanting exactly -EBUSY on a userspace bug are minuscule. Reviewed-by: Tom Lendacky Link: https://lore.kernel.org/r/20240131235609.4161407-5-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'arch/x86/kvm/svm') diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 5f8312edee36..f06f9e51ad9d 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -259,9 +259,8 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) if (kvm->created_vcpus) return -EINVAL; - ret = -EBUSY; if (unlikely(sev->active)) - return ret; + return -EINVAL; sev->active = true; sev->es_active = argp->id == KVM_SEV_ES_INIT; -- cgit v1.2.3