niansa-misc/linux
1
0
Fork 0
mirror of synced 2025-03-06 20:59:54 +01:00
Code Issues Projects Releases Packages Wiki Activity

KVM: arm64: Remove host FPSIMD saving for non-protected KVM

Browse source 
Now that the host eagerly saves its own FPSIMD/SVE/SME state,
non-protected KVM never needs to save the host FPSIMD/SVE/SME state,
and the code to do this is never used. Protected KVM still needs to
save/restore the host FPSIMD/SVE state to avoid leaking guest state to
the host (and to avoid revealing to the host whether the guest used
FPSIMD/SVE/SME), and that code needs to be retained.

Remove the unused code and data structures.

To avoid the need for a stub copy of kvm_hyp_save_fpsimd_host() in the
VHE hyp code, the nVHE/hVHE version is moved into the shared switch
header, where it is only invoked when KVM is in protected mode.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250210195226.1215254-3-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Mark Rutland 2025-02-10 19:52:20 +00:00 • committed by Marc Zyngier
parent fbc7e61195
commit 8eca7f6d51
7 changed files with 28 additions and 63 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
arch/arm64/include/asm/kvm_host.h
View file

@ -624,23 +624,13 @@ struct kvm_host_data {
struct kvm_cpu_context host_ctxt;
/*
* All pointers in this union are hyp VA.
* Hyp VA.
* sve_state is only used in pKVM and if system_supports_sve().
*/
union {
struct user_fpsimd_state *fpsimd_state;
struct cpu_sve_state *sve_state;
};
struct cpu_sve_state *sve_state;
union {
/* HYP VA pointer to the host storage for FPMR */
u64 *fpmr_ptr;
/*
* Used by pKVM only, as it needs to provide storage
* for the host
*/
u64 fpmr;
};
/* Used by pKVM only. */
u64 fpmr;
/* Ownership of the FP regs */
enum {

8
arch/arm64/kvm/arm.c
View file

@ -2481,14 +2481,6 @@ static void finalize_init_hyp_mode(void)
per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->sve_state =
kern_hyp_va(sve_state);
}
} else {
for_each_possible_cpu(cpu) {
struct user_fpsimd_state *fpsimd_state;
fpsimd_state = &per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->host_ctxt.fp_regs;
per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->fpsimd_state =
kern_hyp_va(fpsimd_state);
}
}
}

2
arch/arm64/kvm/fpsimd.c
View file

@ -64,8 +64,6 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
*/
fpsimd_save_and_flush_cpu_state();
*host_data_ptr(fp_owner) = FP_STATE_FREE;
*host_data_ptr(fpsimd_state) = NULL;
*host_data_ptr(fpmr_ptr) = NULL;
host_data_clear_flag(HOST_SVE_ENABLED);
if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)

25
arch/arm64/kvm/hyp/include/hyp/switch.h
View file

@ -375,7 +375,28 @@ static inline void __hyp_sve_save_host(void)
true);
}
static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu);
static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu)
{
/*
* Non-protected kvm relies on the host restoring its sve state.
* Protected kvm restores the host's sve state as not to reveal that
* fpsimd was used by a guest nor leak upper sve bits.
*/
if (system_supports_sve()) {
__hyp_sve_save_host();
/* Re-enable SVE traps if not supported for the guest vcpu. */
if (!vcpu_has_sve(vcpu))
cpacr_clear_set(CPACR_EL1_ZEN, 0);
} else {
__fpsimd_save_state(host_data_ptr(host_ctxt.fp_regs));
}
if (kvm_has_fpmr(kern_hyp_va(vcpu->kvm)))
*host_data_ptr(fpmr) = read_sysreg_s(SYS_FPMR);
}
/*
* We trap the first access to the FP/SIMD to save the host context and
@ -425,7 +446,7 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
isb();
/* Write out the host state if it's in the registers */
if (host_owns_fp_regs())
if (is_protected_kvm_enabled() && host_owns_fp_regs())
kvm_hyp_save_fpsimd_host(vcpu);
/* Restore the guest state */

2
arch/arm64/kvm/hyp/nvhe/hyp-main.c
View file

@ -83,7 +83,7 @@ static void fpsimd_sve_sync(struct kvm_vcpu *vcpu)
if (system_supports_sve())
__hyp_sve_restore_host();
else
__fpsimd_restore_state(*host_data_ptr(fpsimd_state));
__fpsimd_restore_state(host_data_ptr(host_ctxt.fp_regs));
if (has_fpmr)
write_sysreg_s(*host_data_ptr(fpmr), SYS_FPMR);

28
arch/arm64/kvm/hyp/nvhe/switch.c
View file

@ -192,34 +192,6 @@ static bool kvm_handle_pvm_sys64(struct kvm_vcpu *vcpu, u64 *exit_code)
kvm_handle_pvm_sysreg(vcpu, exit_code));
}
static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu)
{
/*
* Non-protected kvm relies on the host restoring its sve state.
* Protected kvm restores the host's sve state as not to reveal that
* fpsimd was used by a guest nor leak upper sve bits.
*/
if (unlikely(is_protected_kvm_enabled() && system_supports_sve())) {
__hyp_sve_save_host();
/* Re-enable SVE traps if not supported for the guest vcpu. */
if (!vcpu_has_sve(vcpu))
cpacr_clear_set(CPACR_EL1_ZEN, 0);
} else {
__fpsimd_save_state(*host_data_ptr(fpsimd_state));
}
if (kvm_has_fpmr(kern_hyp_va(vcpu->kvm))) {
u64 val = read_sysreg_s(SYS_FPMR);
if (unlikely(is_protected_kvm_enabled()))
*host_data_ptr(fpmr) = val;
else
**host_data_ptr(fpmr_ptr) = val;
}
}
static const exit_handler_fn hyp_exit_handlers[] = {
[0 ... ESR_ELx_EC_MAX] = NULL,
[ESR_ELx_EC_CP15_32] = kvm_hyp_handle_cp15_32,

8
arch/arm64/kvm/hyp/vhe/switch.c
View file

@ -413,14 +413,6 @@ static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code)
return true;
}
static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu)
{
__fpsimd_save_state(*host_data_ptr(fpsimd_state));
if (kvm_has_fpmr(vcpu->kvm))
**host_data_ptr(fpmr_ptr) = read_sysreg_s(SYS_FPMR);
}
static bool kvm_hyp_handle_tlbi_el2(struct kvm_vcpu *vcpu, u64 *exit_code)
{
int ret = -EINVAL;