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Wed, 24 Jan 2024 00:48:40 -0800 (PST) Message-ID: Date: Wed, 24 Jan 2024 09:48:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12.2 01/15] vpci: use per-domain PCI lock to protect vpci structure Content-Language: en-US To: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= Cc: Stewart Hildebrand , Oleksandr Andrushchenko , Andrew Cooper , Wei Liu , George Dunlap , Julien Grall , Stefano Stabellini , Jun Nakajima , Kevin Tian , Paul Durrant , Volodymyr Babchuk , xen-devel@lists.xenproject.org References: <20240109215145.430207-1-stewart.hildebrand@amd.com> <20240109215145.430207-2-stewart.hildebrand@amd.com> <20240115194309.45683-1-stewart.hildebrand@amd.com> <715e40c9-1776-4677-9565-dac1565a2aa8@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 23.01.2024 16:07, Roger Pau Monné wrote: > On Tue, Jan 23, 2024 at 03:32:12PM +0100, Jan Beulich wrote: >> On 15.01.2024 20:43, Stewart Hildebrand wrote: >>> @@ -2888,6 +2888,8 @@ int allocate_and_map_msi_pirq(struct domain *d, int index, int *pirq_p, >>> { >>> int irq, pirq, ret; >>> >>> + ASSERT(pcidevs_locked() || rw_is_locked(&d->pci_lock)); >> >> If either lock is sufficient to hold here, ... >> >>> --- a/xen/arch/x86/physdev.c >>> +++ b/xen/arch/x86/physdev.c >>> @@ -123,7 +123,9 @@ int physdev_map_pirq(domid_t domid, int type, int *index, int *pirq_p, >>> >>> case MAP_PIRQ_TYPE_MSI: >>> case MAP_PIRQ_TYPE_MULTI_MSI: >>> + pcidevs_lock(); >>> ret = allocate_and_map_msi_pirq(d, *index, pirq_p, type, msi); >>> + pcidevs_unlock(); >>> break; >> > > IIRC (Stewart can further comment) this is done holding the pcidevs > lock to keep the path unmodified, as there's no need to hold the > per-domain rwlock. Yet why would we prefer to acquire a global lock when a per-domain one suffices? Jan