From 7914695743d598b189d549f2f57af24aa5633705 Mon Sep 17 00:00:00 2001 From: Alexey Kardashevskiy Date: Fri, 20 Jan 2023 14:10:45 +1100 Subject: x86/amd: Cache debug register values in percpu variables Reading DR[0-3]_ADDR_MASK MSRs takes about 250 cycles which is going to be noticeable with the AMD KVM SEV-ES DebugSwap feature enabled. KVM is going to store host's DR[0-3] and DR[0-3]_ADDR_MASK before switching to a guest; the hardware is going to swap these on VMRUN and VMEXIT. Store MSR values passed to set_dr_addr_mask() in percpu variables (when changed) and return them via new amd_get_dr_addr_mask(). The gain here is about 10x. As set_dr_addr_mask() uses the array too, change the @dr type to unsigned to avoid checking for <0. And give it the amd_ prefix to match the new helper as the whole DR_ADDR_MASK feature is AMD-specific anyway. While at it, replace deprecated boot_cpu_has() with cpu_feature_enabled() in set_dr_addr_mask(). Signed-off-by: Alexey Kardashevskiy Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230120031047.628097-2-aik@amd.com --- arch/x86/kernel/hw_breakpoint.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/x86/kernel/hw_breakpoint.c') diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index bbb0f737aab1..b01644c949b2 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -127,7 +127,7 @@ int arch_install_hw_breakpoint(struct perf_event *bp) set_debugreg(*dr7, 7); if (info->mask) - set_dr_addr_mask(info->mask, i); + amd_set_dr_addr_mask(info->mask, i); return 0; } @@ -166,7 +166,7 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp) set_debugreg(dr7, 7); if (info->mask) - set_dr_addr_mask(0, i); + amd_set_dr_addr_mask(0, i); /* * Ensure the write to cpu_dr7 is after we've set the DR7 register. -- cgit v1.2.3