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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id r11sm3119537edt.58.2021.01.28.07.10.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Jan 2021 07:10:26 -0800 (PST) Subject: Re: [PATCH v2 14/14] KVM: SVM: Skip SEV cache flush if no ASIDs have been used To: Sean Christopherson , Dave Hansen , Andy Lutomirski , Peter Zijlstra Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Tom Lendacky , Brijesh Singh References: <20210114003708.3798992-1-seanjc@google.com> <20210114003708.3798992-15-seanjc@google.com> From: Paolo Bonzini Message-ID: <55a63dfb-94a4-6ba2-31d1-c9b6830ff791@redhat.com> Date: Thu, 28 Jan 2021 16:10:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210114003708.3798992-15-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/01/21 01:37, Sean Christopherson wrote: > Skip SEV's expensive WBINVD and DF_FLUSH if there are no SEV ASIDs > waiting to be reclaimed, e.g. if SEV was never used. This "fixes" an > issue where the DF_FLUSH fails during hardware teardown if the original > SEV_INIT failed. Ideally, SEV wouldn't be marked as enabled in KVM if > SEV_INIT fails, but that's a problem for another day. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/svm/sev.c | 22 ++++++++++------------ > 1 file changed, 10 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 23a4bead4a82..e71bc742d8da 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -56,9 +56,14 @@ struct enc_region { > unsigned long size; > }; > > -static int sev_flush_asids(void) > +static int sev_flush_asids(int min_asid, int max_asid) > { > - int ret, error = 0; > + int ret, pos, error = 0; > + > + /* Check if there are any ASIDs to reclaim before performing a flush */ > + pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid); > + if (pos >= max_asid) > + return -EBUSY; > > /* > * DEACTIVATE will clear the WBINVD indicator causing DF_FLUSH to fail, > @@ -80,14 +85,7 @@ static int sev_flush_asids(void) > /* Must be called with the sev_bitmap_lock held */ > static bool __sev_recycle_asids(int min_asid, int max_asid) > { > - int pos; > - > - /* Check if there are any ASIDs to reclaim before performing a flush */ > - pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid); > - if (pos >= max_asid) > - return false; > - > - if (sev_flush_asids()) > + if (sev_flush_asids(min_asid, max_asid)) > return false; > > /* The flush process will flush all reclaimable SEV and SEV-ES ASIDs */ > @@ -1323,10 +1321,10 @@ void sev_hardware_teardown(void) > if (!sev_enabled) > return; > > + sev_flush_asids(0, max_sev_asid); > + > bitmap_free(sev_asid_bitmap); > bitmap_free(sev_reclaim_asid_bitmap); > - > - sev_flush_asids(); > } > > int sev_cpu_init(struct svm_cpu_data *sd) > I can't find 00/14 in my inbox, so: queued 1-3 and 6-14, thanks. Paolo