Commit 9bc36635 authored by Hou Wenlong's avatar Hou Wenlong Committed by Sean Christopherson
Browse files

KVM: x86: Add helper to retrieve current value of user return MSR 



In the user return MSR support, the cached value is always the hardware
value of the specific MSR. Therefore, add a helper to retrieve the
cached value, which can replace the need for RDMSR, for example, to
allow SEV-ES guests to restore the correct host hardware value without
using RDMSR.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarHou Wenlong <houwenlong.hwl@antgroup.com>
[sean: drop "cache" from the name, make it a one-liner, tag for stable]
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20250923153738.1875174-2-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 5b66e335

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -2357,6 +2357,7 @@ int kvm_add_user_return_msr(u32 msr); 
int kvm_find_user_return_msr(u32 msr);

int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask);

void kvm_user_return_msr_update_cache(unsigned int index, u64 val);

u64 kvm_get_user_return_msr(unsigned int slot);



static inline bool kvm_is_supported_user_return_msr(u32 msr)

{

arch/x86/kvm/x86.c

+6 −0
Original line number Diff line number Diff line
@@ -677,6 +677,12 @@ void kvm_user_return_msr_update_cache(unsigned int slot, u64 value) 
}

EXPORT_SYMBOL_GPL(kvm_user_return_msr_update_cache);



u64 kvm_get_user_return_msr(unsigned int slot)

{

	return this_cpu_ptr(user_return_msrs)->values[slot].curr;

}

EXPORT_SYMBOL_GPL(kvm_get_user_return_msr);



static void drop_user_return_notifiers(void)

{

	struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs);