On Thu, Jul 22, 2021, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@xxxxxxx>
>
> Replace the get function with macros and the set function with
> hypercall specific setters. This will avoid preserving any previous
> bits in the GHCB-MSR and improved code readability.
>
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> arch/x86/include/asm/sev-common.h | 9 +++++++
> arch/x86/kvm/svm/sev.c | 41 +++++++++++--------------------
> 2 files changed, 24 insertions(+), 26 deletions(-)
>
> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> index 2cef6c5a52c2..8540972cad04 100644
> --- a/arch/x86/include/asm/sev-common.h
> +++ b/arch/x86/include/asm/sev-common.h
> @@ -50,6 +50,10 @@
> (GHCB_MSR_CPUID_REQ | \
> (((unsigned long)reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS) | \
> (((unsigned long)fn) << GHCB_MSR_CPUID_FUNC_POS))
> +#define GHCB_MSR_CPUID_FN(msr) \
> + (((msr) >> GHCB_MSR_CPUID_FUNC_POS) & GHCB_MSR_CPUID_FUNC_MASK)
> +#define GHCB_MSR_CPUID_REG(msr) \
> + (((msr) >> GHCB_MSR_CPUID_REG_POS) & GHCB_MSR_CPUID_REG_MASK)
>
> /* AP Reset Hold */
> #define GHCB_MSR_AP_RESET_HOLD_REQ 0x006
> @@ -67,6 +71,11 @@
> #define GHCB_SEV_TERM_REASON(reason_set, reason_val) \
> (((((u64)reason_set) & GHCB_MSR_TERM_REASON_SET_MASK) << GHCB_MSR_TERM_REASON_SET_POS) | \
> ((((u64)reason_val) & GHCB_MSR_TERM_REASON_MASK) << GHCB_MSR_TERM_REASON_POS))
> +#define GHCB_MSR_TERM_REASON_SET(msr) \
> + (((msr) >> GHCB_MSR_TERM_REASON_SET_POS) & GHCB_MSR_TERM_REASON_SET_MASK)
> +#define GHCB_MSR_TERM_REASON(msr) \
> + (((msr) >> GHCB_MSR_TERM_REASON_POS) & GHCB_MSR_TERM_REASON_MASK)
> +
>
> #define GHCB_SEV_ES_REASON_GENERAL_REQUEST 0
> #define GHCB_SEV_ES_REASON_PROTOCOL_UNSUPPORTED 1
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 6710d9ee2e4b..d7b3557b8dbb 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2342,16 +2342,15 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
> return true;
> }
>
> -static void set_ghcb_msr_bits(struct vcpu_svm *svm, u64 value, u64 mask,
> - unsigned int pos)
> +static void set_ghcb_msr_cpuid_resp(struct vcpu_svm *svm, u64 reg, u64 value)
> {
> - svm->vmcb->control.ghcb_gpa &= ~(mask << pos);
> - svm->vmcb->control.ghcb_gpa |= (value & mask) << pos;
> -}
> + u64 msr;
>
> -static u64 get_ghcb_msr_bits(struct vcpu_svm *svm, u64 mask, unsigned int pos)
> -{
> - return (svm->vmcb->control.ghcb_gpa >> pos) & mask;
> + msr = GHCB_MSR_CPUID_RESP;
> + msr |= (reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS;
> + msr |= (value & GHCB_MSR_CPUID_VALUE_MASK) << GHCB_MSR_CPUID_VALUE_POS;
> +
> + svm->vmcb->control.ghcb_gpa = msr;
I would rather have the get/set pairs be roughly symmetric, i.e. both functions
or both macros, and both work on svm->vmcb->control.ghcb_gpa or both be purely
functional (that may not be the correct word).
I don't have a strong preference on function vs. macro. But for the second one,
my preference would be to have the helper generate the value as opposed to taken
and filling a pointer, e.g. to yield something like:
cpuid_reg = GHCB_MSR_CPUID_REG(control->ghcb_gpa);
if (cpuid_reg == 0)
cpuid_value = vcpu->arch.regs[VCPU_REGS_RAX];
else if (cpuid_reg == 1)
cpuid_value = vcpu->arch.regs[VCPU_REGS_RBX];
else if (cpuid_reg == 2)
cpuid_value = vcpu->arch.regs[VCPU_REGS_RCX];
else
cpuid_value = vcpu->arch.regs[VCPU_REGS_RDX];
control->ghcb_gpa = MAKE_GHCB_MSR_RESP(cpuid_reg, cpuid_value);
The advantage is that it's obvious from the code that control->ghcb_gpa is being
read _and_ written.
> case GHCB_MSR_TERM_REQ: {
> u64 reason_set, reason_code;
>
> - reason_set = get_ghcb_msr_bits(svm,
> - GHCB_MSR_TERM_REASON_SET_MASK,
> - GHCB_MSR_TERM_REASON_SET_POS);
> - reason_code = get_ghcb_msr_bits(svm,
> - GHCB_MSR_TERM_REASON_MASK,
> - GHCB_MSR_TERM_REASON_POS);
> + reason_set = GHCB_MSR_TERM_REASON_SET(control->ghcb_gpa);
> + reason_code = GHCB_MSR_TERM_REASON(control->ghcb_gpa);
> +
> pr_info("SEV-ES guest requested termination: %#llx:%#llx\n",
> reason_set, reason_code);
> +
> fallthrough;
Not related to this patch, but why use fallthrough and more importantly, why is
this an -EINVAL return? Why wouldn't KVM forward the request to userspace instead
of returning an opaque -EINVAL?
> }
> default:
> --
> 2.31.1
>
