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Tue, 23 Jul 2024 03:02:11 -0700 (PDT) Message-ID: <14ffb00d-d6ba-4c18-88c1-2601a2df8a8b@suse.com> Date: Tue, 23 Jul 2024 12:02:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/8] xen/riscv: introduce asm/pmap.h header To: oleksii.kurochko@gmail.com Cc: Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Stefano Stabellini , xen-devel@lists.xenproject.org, Julien Grall References: <6458c61d-5974-41c2-a1e6-76e4a15a487a@suse.com> <54af6fb751da1103054de2d79a2057bec658f399.camel@gmail.com> <623da862-8e76-4d40-9aa9-b02c8fd9944d@xen.org> <26ae01e2-d085-48d7-8b1f-da1e44b01e53@xen.org> <97c82aca-0b8a-4b78-980b-0857dbdae80a@suse.com> <4c9eb7a79c33c7cd2f6bde05b1fbc7770e662026.camel@gmail.com> Content-Language: en-US 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: <4c9eb7a79c33c7cd2f6bde05b1fbc7770e662026.camel@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 23.07.2024 10:55, oleksii.kurochko@gmail.com wrote: > On Tue, 2024-07-23 at 10:36 +0200, Jan Beulich wrote: >> On 23.07.2024 10:02, Oleksii Kurochko wrote: >>> On Mon, Jul 22, 2024 at 7:27 PM Julien Grall >>> wrote: >>>>>> On 22/07/2024 15:44, Oleksii Kurochko wrote: >>>>>     /* Map a 4k page in a fixmap entry */ >>>>>     void set_fixmap(unsigned map, mfn_t mfn, unsigned int >>>>> flags) >>>>>     { >>>>>         pte_t pte; >>>>> >>>>>         pte = mfn_to_xen_entry(mfn, flags); >>>>>         pte.pte |= PTE_LEAF_DEFAULT; >>>>>         write_pte(&xen_fixmap[pt_index(0, FIXMAP_ADDR(map))], >>>>> pte); >>>> >>>> It would be saner to check if you are not overwriting any >>>> existing >>>> mapping as otherwise you will probably need a TLB flush. >>>> >>>>>     } >>>>> >>>>>     /* Remove a mapping from a fixmap entry */ >>>>>     void clear_fixmap(unsigned map) >>>>>     { >>>>>         pte_t pte = {0}; >>>>>         write_pte(&xen_fixmap[pt_index(0, FIXMAP_ADDR(map))], >>>>> pte); >>>> >>>> Don't you need a TLB flush? >>>> >>> Inside write_pte() there is "sfence.vma". >> >> That's just a fence though, not a TLB flush. > From the privileged doc: > ``` > SFENCE.VMA is also used to invalidate entries in the > address-translation cache associated with a hart (see Section 4.3.2). > ... > The SFENCE.VMA is used to flush any local hardware caches related to > address translation. > It is specified as a fence rather than a TLB flush to provide cleaner > semantics with respect to > which instructions are affected by the flush operation and to support a > wider variety of dynamic > caching structures and memory-management schemes. SFENCE.VMA is also > used by higher > privilege levels to synchronize page table writes and the address > translation hardware. > ... > ``` > I read this as SFENCE.VMA is used not only for ordering of load/stores, > but also to flush TLB ( which is a type of more general term as > address-translation cache, IIUIC ). Oh, I see. Kind of unexpected for an instruction of that name. Yet note how they talk about the local hart only. You need a wider scope TLB flush here. Jan