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[92.178.7.112]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-4532e24155bsm11400615e9.17.2025.06.12.00.32.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jun 2025 00:32:35 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 6af48e3c-475f-11f0-b894-0df219b8e170 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1749713558; x=1750318358; darn=lists.xenproject.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=4gAWW7lVm7WQQuR9+ND31YNRD8GoyHuETasTztULC8s=; b=lYIcOB0KHK11ncanm7v7P0Hbofy9CG07tavpsrJ94xOpm7Wex9sOA/tzoNK57iC0HS uw77yu9+abOrS2lLHp5kAOtSFruGETHbbBKq4a6pdg9QDdme0MxU73VlaP8Xa1WmXSwj QmTYzxyuP9uLWRY/sKeblD/yfDIIq2O15ZfF0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749713558; x=1750318358; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=4gAWW7lVm7WQQuR9+ND31YNRD8GoyHuETasTztULC8s=; b=j8MK9H9Lgb4JYKVkp5BrXRhZASae+0ARucyIm3Wb+2PUFxkD1dxisVRqRQVaVbcRVd EpbrHwNxL2a5yOb7BMvdlHFLyjMijDwGwTlyvd12CVsA7dduTVmm07G0PJEs3lV35Z+s 9M2iom9DnV8Y61ZUipNbDvhlRX6dZQZ4HrNoZkWrVWAuzhFXpvzZPW//CRDshma6pDo7 cgS3/Z2hc5vSrnvzZCGNrMT2PxOVm5tfwyOOX0i4GBretU/RhZ0nxkEC47Pb5+VtjfIu 69xeszfkKk0ViUX7mduXtc3gmi6Cpa7wqCqIbnILQ8TRdQNXwVWkfINJmL/a1ZCZNOPV IQYQ== X-Forwarded-Encrypted: i=1; AJvYcCXP4C8uH4Sb+Ei+CPbx/RZiPJpgLEGPiNfvC1VKhThqYvDZB2DFbl6Wo5ZeK6oIgTzZfnFb3NFNux0=@lists.xenproject.org X-Gm-Message-State: AOJu0YxxA1KKsEzM5WhP8SfJmDS1No/VkeZv9Ib7e1oOdYpBeFGR0ec9 c31NfXmVJUVHHTIEj3zF2um/cozXiWc5bfVyKc80aV0W2bSe26XR/2/4zBAyoyQ8XHA= X-Gm-Gg: ASbGnctINOsxV4Z/N4U4koeuP67+FI8nlZoOrhO9gN8X5mSHRFqUyPzzX7jor6QN68c uYI5E7Ynh978BC+pTm2psKeFKbeqDI2RNs0Voyi6CZwz5IGmbXXZSPhDVyCrIvgwLZpKZ9TosNB QQjKgYF1wkDrUpYUQfd8KstEJb3hB0KWM53wooCv6lZBQrlMaUrOXwD1Gfh9djOzTCcOOGjQAOI n38oCjwVLdrjejHcc0ets+6cvNkf7T+bHKG0lTziiWGmklWb8n9B9C4QyzpJ7C0G0jN8YRHTOCd 3x368vkVZ0Q3+slYihGhN9S0y7kPEY1YZ/90awBZevBcUGPB2zb5PgK5knhgvVCa5bL/iVk62+F YDXd2XG6oiGQARssb4nQdMmwsu47C1w== X-Google-Smtp-Source: AGHT+IGIDmpe/vpgG2F89wY0phShV8ZgXmKnmN499GI0gkWUeVkx7U6geXhTpUnzjdYW8T2K585Uaw== X-Received: by 2002:a05:600c:138e:b0:442:e147:bea7 with SMTP id 5b1f17b1804b1-4532d368101mr17510785e9.29.1749713555860; Thu, 12 Jun 2025 00:32:35 -0700 (PDT) Date: Thu, 12 Jun 2025 09:32:34 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: Stewart Hildebrand , xen-devel@lists.xenproject.org Subject: Re: [PATCH v1 5/5] vpci: allow 32-bit BAR writes with memory decoding enabled Message-ID: References: <20250531125405.268984-1-stewart.hildebrand@amd.com> <20250531125405.268984-6-stewart.hildebrand@amd.com> <9ec5079f-9bc1-4843-a266-d74bf0556619@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <9ec5079f-9bc1-4843-a266-d74bf0556619@suse.com> On Thu, Jun 05, 2025 at 12:41:06PM +0200, Jan Beulich wrote: > On 31.05.2025 14:54, Stewart Hildebrand wrote: > > Currently, Xen vPCI refuses BAR writes if the BAR is mapped in p2m. If > > firmware initializes a 32-bit BAR to a bad address, Linux may try to > > write a new address to the BAR without disabling memory decoding. Since > > Xen refuses such writes, the BAR (and thus PCI device) will be > > non-functional. > > Doing this for 32-bit BARs only, with not even an outline what to do about > the same issue with 64-bit ones, seems like it won't buy us very much. IIRC Linux will disable decoding in the common case when updating the position of a 64bit BAR. However it won't disable decoding for 32bit BARs. I think that's why Stewart cares more about the 32bit case than the 64bit one. Regards, Roger.