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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id c9sm8863667wrr.78.2021.03.12.10.18.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Mar 2021 10:18:43 -0800 (PST) Subject: Re: [PATCH v4] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Brijesh Singh References: <1614130683-24137-1-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: Date: Fri, 12 Mar 2021 19:18:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <1614130683-24137-1-git-send-email-wanpengli@tencent.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 24/02/21 02:37, Wanpeng Li wrote: > From: Wanpeng Li > > # lscpu > Architecture: x86_64 > CPU op-mode(s): 32-bit, 64-bit > Byte Order: Little Endian > CPU(s): 88 > On-line CPU(s) list: 0-63 > Off-line CPU(s) list: 64-87 > > # cat /proc/cmdline > BOOT_IMAGE=/vmlinuz-5.10.0-rc3-tlinux2-0050+ root=/dev/mapper/cl-root ro > rd.lvm.lv=cl/root rhgb quiet console=ttyS0 LANG=en_US .UTF-8 no-kvmclock-vsyscall > > # echo 1 > /sys/devices/system/cpu/cpu76/online > -bash: echo: write error: Cannot allocate memory > > The per-cpu vsyscall pvclock data pointer assigns either an element of the > static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory > hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if > kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in > kvmclock_setup_percpu() which returns -ENOMEM. It's broken for no-vsyscall > and sometimes you end up with vsyscall disabled if the host does something > strange. This patch fixes it by allocating this dynamically memory > unconditionally even if vsyscall is disabled. > > Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables") > Reported-by: Zelin Deng > Cc: Brijesh Singh > Cc: stable@vger.kernel.org#v4.19-rc5+ > Signed-off-by: Wanpeng Li > --- > v3 -> v4: > * fix kernel test robot report WARNING > v2 -> v3: > * allocate dynamically memory unconditionally > v1 -> v2: > * add code comments > > arch/x86/kernel/kvmclock.c | 19 +++++++++---------- > 1 file changed, 9 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index aa59374..1fc0962 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -268,21 +268,20 @@ static void __init kvmclock_init_mem(void) > > static int __init kvm_setup_vsyscall_timeinfo(void) > { > -#ifdef CONFIG_X86_64 > - u8 flags; > + kvmclock_init_mem(); > > - if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall) > - return 0; > +#ifdef CONFIG_X86_64 > + if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) { > + u8 flags; > > - flags = pvclock_read_flags(&hv_clock_boot[0].pvti); > - if (!(flags & PVCLOCK_TSC_STABLE_BIT)) > - return 0; > + flags = pvclock_read_flags(&hv_clock_boot[0].pvti); > + if (!(flags & PVCLOCK_TSC_STABLE_BIT)) > + return 0; > > - kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK; > + kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK; > + } > #endif > > - kvmclock_init_mem(); > - > return 0; > } > early_initcall(kvm_setup_vsyscall_timeinfo); > Queued, thanks. Paolo