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KVM: arm64: Avoid reading ID_AA64DFR0_EL1 for debug save/restore

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Similar to other per-CPU profiling/debug features we handle, store the
number of breakpoints/watchpoints in kvm_host_data to avoid reading the
ID register 4 times on every guest entry/exit. And if you're in the
nested virt business that's quite a few avoidable exits to the L0
hypervisor.

Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241219224116.3941496-18-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Oliver Upton
2024-12-19 14:41:14 -08:00
committed by Marc Zyngier
parent b0ee51033a
commit 8c02c2bbd6
3 changed files with 11 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/arm64/include/asm/kvm_host.h
+4
View File
@@ -661,6 +661,10 @@ struct kvm_host_data {
/* Number of programmable event counters (PMCR_EL0.N) for this CPU */
unsigned int nr_event_counters;
/* Number of debug breakpoints/watchpoints for this CPU (minus 1) */
unsigned int debug_brps;
unsigned int debug_wrps;
};
struct kvm_host_psci_config {
arch/arm64/kvm/debug.c
+3
View File
@@ -71,6 +71,9 @@ void kvm_init_host_debug_data(void)
*host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N,
read_sysreg(pmcr_el0));
*host_data_ptr(debug_brps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0);
*host_data_ptr(debug_wrps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0);
if (has_vhe())
return;
arch/arm64/kvm/hyp/include/hyp/debug-sr.h
+4 -13
View File
@@ -106,12 +106,8 @@ static struct kvm_guest_debug_arch *__vcpu_debug_regs(struct kvm_vcpu *vcpu)
static void __debug_save_state(struct kvm_guest_debug_arch *dbg,
struct kvm_cpu_context *ctxt)
{
u64 aa64dfr0;
int brps, wrps;
aa64dfr0 = read_sysreg(id_aa64dfr0_el1);
brps = (aa64dfr0 >> 12) & 0xf;
wrps = (aa64dfr0 >> 20) & 0xf;
int brps = *host_data_ptr(debug_brps);
int wrps = *host_data_ptr(debug_wrps);
save_debug(dbg->dbg_bcr, dbgbcr, brps);
save_debug(dbg->dbg_bvr, dbgbvr, brps);
@@ -124,13 +120,8 @@ static void __debug_save_state(struct kvm_guest_debug_arch *dbg,
static void __debug_restore_state(struct kvm_guest_debug_arch *dbg,
struct kvm_cpu_context *ctxt)
{
u64 aa64dfr0;
int brps, wrps;
aa64dfr0 = read_sysreg(id_aa64dfr0_el1);
brps = (aa64dfr0 >> 12) & 0xf;
wrps = (aa64dfr0 >> 20) & 0xf;
int brps = *host_data_ptr(debug_brps);
int wrps = *host_data_ptr(debug_wrps);
restore_debug(dbg->dbg_bcr, dbgbcr, brps);
restore_debug(dbg->dbg_bvr, dbgbvr, brps);