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[91.219.240.8]) by smtp.gmail.com with ESMTPSA id pa29-20020a05620a831d00b0074d3233487dsm182509qkn.114.2023.06.08.01.54.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jun 2023 01:54:57 -0700 (PDT) From: Vitaly Kuznetsov To: Tianyu Lan , kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, daniel.lezcano@linaro.org, arnd@arndb.de, michael.h.kelley@microsoft.com Cc: Tianyu Lan , linux-arch@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/9] drivers: hv: Mark shared pages unencrypted in SEV-SNP enlightened guest In-Reply-To: <2803e5d6-58bc-57f1-0721-226333238883@gmail.com> References: <20230601151624.1757616-1-ltykernel@gmail.com> <20230601151624.1757616-5-ltykernel@gmail.com> <87zg5ejchp.fsf@redhat.com> <2803e5d6-58bc-57f1-0721-226333238883@gmail.com> Date: Thu, 08 Jun 2023 10:54:53 +0200 Message-ID: <87cz26jpuq.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org Tianyu Lan writes: > On 6/5/2023 8:54 PM, Vitaly Kuznetsov wrote: >>> @@ -402,7 +417,14 @@ int hv_common_cpu_die(unsigned int cpu) >>> >>> local_irq_restore(flags); >>> >>> - kfree(mem); >>> + if (hv_isolation_type_en_snp()) { >>> + ret = set_memory_encrypted((unsigned long)mem, pgcount); >>> + if (ret) >>> + pr_warn("Hyper-V: Failed to encrypt input arg on cpu%d: %d\n", >>> + cpu, ret); >>> + /* It's unsafe to free 'mem'. */ >>> + return 0; >> Why is it unsafe to free 'mem' if ret == 0? Also, why don't we want to >> proparate non-zero 'ret' from here to fail CPU offlining? >> > > Based on Michael's patch the mem will not be freed during cpu offline. > https://lwn.net/ml/linux-kernel/87cz2j5zrc.fsf@redhat.com/ > So I think it's unnessary to encrypt the mem again here. Good, you can probably include Michael's patch in your next submission then (unless it gets merged before that). -- Vitaly