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Mon, 20 May 2024 23:21:32 -0700 (PDT) Message-ID: Date: Tue, 21 May 2024 08:21:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/12] IOMMU: rename and re-type ats_enabled Content-Language: en-US To: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= Cc: "xen-devel@lists.xenproject.org" , Paul Durrant References: <64b028be-2197-4951-ae5b-32f9eabfa84a@suse.com> <7f11ca06-9bed-443b-9c79-0e62b71a1f96@suse.com> <24d52bbb-1329-4f8a-81be-505a35969875@suse.com> <44af358a-9510-4056-826c-3be99dc25830@suse.com> From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 20.05.2024 12:29, Roger Pau Monné wrote: > On Wed, May 15, 2024 at 12:07:50PM +0200, Jan Beulich wrote: >> On 06.05.2024 15:53, Roger Pau Monné wrote: >>> On Mon, May 06, 2024 at 03:20:38PM +0200, Jan Beulich wrote: >>>> On 06.05.2024 14:42, Roger Pau Monné wrote: >>>>> On Thu, Feb 15, 2024 at 11:15:39AM +0100, Jan Beulich wrote: >>>>>> @@ -196,7 +196,7 @@ static int __must_check amd_iommu_setup_ >>>>>> dte->sys_mgt = MASK_EXTR(ivrs_dev->device_flags, ACPI_IVHD_SYSTEM_MGMT); >>>>>> >>>>>> if ( use_ats(pdev, iommu, ivrs_dev) ) >>>>>> - dte->i = ats_enabled; >>>>>> + dte->i = true; >>>>> >>>>> Might be easier to just use: >>>>> >>>>> dte->i = use_ats(pdev, iommu, ivrs_dev); >>>> >>>> I'm hesitant here, as in principle we might be overwriting a "true" by >>>> "false" then. >>> >>> Hm, but that would be fine, what's the point in enabling the IOMMU to >>> reply to ATS requests if ATS is not enabled on the device? >>> >>> IOW: overwriting a "true" with a "false" seem like the correct >>> behavior if it's based on the output of use_ats(). >> >> I don't think so, unless there were flow guarantees excluding the possibility >> of taking this path twice without intermediately disabling the device again. >> Down from here the enabling of ATS is gated on use_ats(). Hence if, in an >> earlier invocation, we enabled ATS (and set dte->i), we wouldn't turn off ATS >> below (there's only code to turn it on), yet with what you suggest we'd clear >> dte->i. > > Please bear with me, I think I'm confused, why would use_ats(), and if > that's the case, don't we want to update dte->i so that it matches the > ATS state? I'm afraid I can't parse this. Maybe a result of incomplete editing? The topic is complex enough that I don't want to even try to guess what you may have meant to ask ... > Otherwise we would fail to disable IOMMU device address translation > support if ATS was disabled? I think the answer here is "no", but with the above I'm not really sure here, either. Jan