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Message-ID: <89efe8fb-6495-5634-9378-a7dbb57f9d81@amd.com>
Date: Mon, 11 Jan 2021 11:57:03 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH 11/13] KVM: SVM: Drop redundant svm_sev_enabled() helper
On 1/8/21 6:47 PM, Sean Christopherson wrote:
> Replace calls to svm_sev_enabled() with direct checks on sev_enabled, or
> in the case of svm_mem_enc_op, simply drop the call to svm_sev_enabled().
> This effectively replaces checks against a valid max_sev_asid with checks
> against sev_enabled. sev_enabled is forced off by sev_hardware_setup()
> if max_sev_asid is invalid, all call sites are guaranteed to run after
> sev_hardware_setup(), and all of the checks care about SEV being fully
> enabled (as opposed to intentionally handling the scenario where
> max_sev_asid is valid but SEV enabling fails due to OOM).
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> arch/x86/kvm/svm/sev.c | 6 +++---
> arch/x86/kvm/svm/svm.h | 5 -----
> 2 files changed, 3 insertions(+), 8 deletions(-)
>
With CONFIG_KVM=y, CONFIG_KVM_AMD=y and CONFIG_CRYPTO_DEV_CCP_DD=m, I get
the following build warning:
make: Entering directory '/root/kernels/kvm-build-x86_64'
DESCEND objtool
CALL scripts/atomic/check-atomics.sh
CALL scripts/checksyscalls.sh
CHK include/generated/compile.h
CC arch/x86/kvm/svm/svm.o
CC arch/x86/kvm/svm/nested.o
CC arch/x86/kvm/svm/avic.o
CC arch/x86/kvm/svm/sev.o
In file included from ./include/linux/cpumask.h:12,
from ./arch/x86/include/asm/cpumask.h:5,
from ./arch/x86/include/asm/msr.h:11,
from ./arch/x86/include/asm/processor.h:22,
from ./arch/x86/include/asm/cpufeature.h:5,
from ./arch/x86/include/asm/thread_info.h:53,
from ./include/linux/thread_info.h:38,
from ./arch/x86/include/asm/preempt.h:7,
from ./include/linux/preempt.h:78,
from ./include/linux/percpu.h:6,
from ./include/linux/context_tracking_state.h:5,
from ./include/linux/hardirq.h:5,
from ./include/linux/kvm_host.h:7,
from arch/x86/kvm/svm/sev.c:11:
In function ‘bitmap_zero’,
inlined from ‘__sev_recycle_asids’ at arch/x86/kvm/svm/sev.c:92:2,
inlined from ‘sev_asid_new’ at arch/x86/kvm/svm/sev.c:113:16,
inlined from ‘sev_guest_init’ at arch/x86/kvm/svm/sev.c:195:9:
./include/linux/bitmap.h:238:2: warning: argument 1 null where non-null expected [-Wnonnull]
238 | memset(dst, 0, len);
| ^~~~~~~~~~~~~~~~~~~
In file included from ./arch/x86/include/asm/string.h:5,
from ./include/linux/string.h:20,
from ./include/linux/bitmap.h:9,
from ./include/linux/cpumask.h:12,
from ./arch/x86/include/asm/cpumask.h:5,
from ./arch/x86/include/asm/msr.h:11,
from ./arch/x86/include/asm/processor.h:22,
from ./arch/x86/include/asm/cpufeature.h:5,
from ./arch/x86/include/asm/thread_info.h:53,
from ./include/linux/thread_info.h:38,
from ./arch/x86/include/asm/preempt.h:7,
from ./include/linux/preempt.h:78,
from ./include/linux/percpu.h:6,
from ./include/linux/context_tracking_state.h:5,
from ./include/linux/hardirq.h:5,
from ./include/linux/kvm_host.h:7,
from arch/x86/kvm/svm/sev.c:11:
arch/x86/kvm/svm/sev.c: In function ‘sev_guest_init’:
./arch/x86/include/asm/string_64.h:18:7: note: in a call to function ‘memset’ declared here
18 | void *memset(void *s, int c, size_t n);
| ^~~~~~
Thanks,
Tom
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 8c34c467a09d..1b9174a49b65 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1052,7 +1052,7 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> struct kvm_sev_cmd sev_cmd;
> int r;
>
> - if (!svm_sev_enabled() || !sev_enabled)
> + if (!sev_enabled)
> return -ENOTTY;
>
> if (!argp)
> @@ -1314,7 +1314,7 @@ void __init sev_hardware_setup(void)
>
> void sev_hardware_teardown(void)
> {
> - if (!svm_sev_enabled())
> + if (!sev_enabled)
> return;
>
> bitmap_free(sev_asid_bitmap);
> @@ -1325,7 +1325,7 @@ void sev_hardware_teardown(void)
>
> int sev_cpu_init(struct svm_cpu_data *sd)
> {
> - if (!svm_sev_enabled())
> + if (!sev_enabled)
> return 0;
>
> sd->sev_vmcbs = kmalloc_array(max_sev_asid + 1, sizeof(void *),
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 4eb4bab0ca3e..8cb4395b58a0 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -569,11 +569,6 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
>
> extern unsigned int max_sev_asid;
>
> -static inline bool svm_sev_enabled(void)
> -{
> - return IS_ENABLED(CONFIG_KVM_AMD_SEV) ? max_sev_asid : 0;
> -}
> -
> void sev_vm_destroy(struct kvm *kvm);
> int svm_mem_enc_op(struct kvm *kvm, void __user *argp);
> int svm_register_enc_region(struct kvm *kvm,
>
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