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Tue, 9 Jul 2024 13:21:00 +0000 Received: from EX19MTAUEC001.ant.amazon.com (10.252.135.222) by EX19D008UEC001.ant.amazon.com (10.252.135.232) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.34; Tue, 9 Jul 2024 13:21:00 +0000 Received: from ua2d7e1a6107c5b.ant.amazon.com (172.19.88.180) by mail-relay.amazon.com (10.252.135.200) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.34 via Frontend Transport; Tue, 9 Jul 2024 13:20:57 +0000 From: Patrick Roy To: , , , , , CC: Patrick Roy , , , , , , , , , , , , , , , , , Subject: [RFC PATCH 2/8] kvm: use slowpath in gfn_to_hva_cache if memory is private Date: Tue, 9 Jul 2024 14:20:30 +0100 Message-ID: <20240709132041.3625501-3-roypat@amazon.co.uk> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240709132041.3625501-1-roypat@amazon.co.uk> References: <20240709132041.3625501-1-roypat@amazon.co.uk> MIME-Version: 1.0 X-Stat-Signature: w1ehet1h5h3fkzh16im3gtnxqom9pcwc X-Rspamd-Queue-Id: DD2E910001A X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1720531262-351064 X-HE-Meta: U2FsdGVkX1/8oC29ARNtNO549rqknBzbVvRa2jUTKPSytTF9LsfJoX+XSd7X2dJGYAMs4jOS0h0qVgessklK2OyriPX/lCVsQsPn7MJOr1A90j1Z68HefTGDTVMzPu8SHtYu5iuXXWjnZ+M9yr19Ix4xWO3Yh7brPYmCJZrPD4dRyAMSqly3VwWdiZRboNZbyeI0ItlTt2TDykpMu3XD4MyDagdSNQ8A39L/WSziUGg9Apl+6iJ/OvudGRWZo28F4yzoNBR2den40RRW4vTfbiaat4D3bf0kh35+oNupISYrSZ2s+NKd6BWE+iE+/gLGRWGiAy98XO+eodVNxdhNp83Z+s243+FNExyERXn7y1nUVIdURX9KPG4b6b6+Xb83yEjGFPCS0uO0lGCSEmPqYZbwJCl/yf0XHufngsoDKVQxW7/lGd4fTfYIx/3rNheVL2GnUzO+IFrWaUEao67a+e0xR+uzt0GLCCqvZal6V2dUbnmUZ/ATlvPd244faH13in8v7+KKrxc8/prIFS6XO1hJ4ckYJ0bGkrd5hPS5iKokUyyazA4IncZ+0uUv+9x5lCoKdBhg3YM7Q1z3wxHu5o3mNf0uTHzfsPYuCZ1BCh+YH/dRksm4guqi8rlFIom67soB53ROeF/04gSZrwdrKl1HjY5vc8yAhbVGq0zCbK5X/d2cxecON3GzmAl6xf4h7aWSWSKQozC+VLhaYxul/DC2B1hbYxnOIQc4nYLrql58CsEe8XcsY5W0v84w/OmiSv1uUbKHR2pDoWA7nt6zdL+m5a2dgMXdAPJ3nJ30jh+pE4tzEM4yA8gObOcVCjGl020+NMQpGaa8/bDxNwlu6BdyRPxAGfhaUSvIHwPbJVo3VUkwdJ30utm/xkOxB2jPH3owPZgx0ibZTqJ3Cle6yrFMEx1GPleXwU6xZx04CL2zytnaWY6krYkVWPVV7S6T1++MBvb2nyH+OP7JHGe rHnVuS+o huyEtpoeWjRD5NVM8CplHXqTcXCBIDsr5eYjgijNwjHdhVKaQPs+MQrxcMsUIAsvPTmcOcwRHau0BTGtBn0h9EATwUtsssxvkB0jwbMjAdvjLCey7mK0ukQGhc7Pv342iJsUI6LgS6sDiiFLMYm7saK1JPWu/2P3lMvkZ74DAHVWGWrFVFOVPPDeLvCYh5igeM7t+shplfTWA/aeyxbYxCPqWFRAD1HhumwwiR/IKUXizwPUFVx4iGKvpGFBeVGV5l9FnAoWA8ITuQlBL0FpSY2h8qLDLHZwG6lu1rp8dlntVkSFPEfWvPwR3YLedGl+9Q3HeyclR1WnEkuok2zQuF6HmRy4j0Ro/ThpdSAzEQuewT8lFIcl/sfjsv/PBypUzzHw0xVHxO6Rk3WtMKCKiBQ7oAf8LBTvq87zOY4AzaTvWgQfr4nysH2+3L9YC9oW2Zhaa X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently, KVM uses gfn_to_hva_caches to cache gfn->memslot->userspace host virtual address (uhva) translations. If a gfn is backed by guest_memfd however, there is no uhva-equivalent item we could possible cache, since accesses go through a file descriptor instead of a VMA. Thus, we effectively disable gfn_to_hva_caches in the case where gfns are gmem-backed, and instead do a gfn->pfn translation on the fly by calling `kvm_{read,write}_guest` inside `kvm_{read,write}_guest_cached`. Signed-off-by: Patrick Roy --- virt/kvm/kvm_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b3b3de70a4df..4357f7cdf040 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3603,7 +3603,7 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc, if (kvm_is_error_hva(ghc->hva)) return -EFAULT; - if (unlikely(!ghc->memslot)) + if (unlikely(!ghc->memslot || kvm_mem_is_private(kvm, gpa_to_gfn(gpa)))) return kvm_write_guest(kvm, gpa, data, len); r = __copy_to_user((void __user *)ghc->hva + offset, data, len); @@ -3641,7 +3641,7 @@ int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc, if (kvm_is_error_hva(ghc->hva)) return -EFAULT; - if (unlikely(!ghc->memslot)) + if (unlikely(!ghc->memslot || kvm_mem_is_private(kvm, gpa_to_gfn(gpa)))) return kvm_read_guest(kvm, gpa, data, len); r = __copy_from_user(data, (void __user *)ghc->hva + offset, len);