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Mon, 27 Jan 2025 02:24:19 -0800 (PST) Message-ID: Date: Mon, 27 Jan 2025 11:24:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 3/3] xen/riscv: update mfn calculation in pt_mapping_level() To: Oleksii Kurochko Cc: Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini , xen-devel@lists.xenproject.org References: 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 20.01.2025 17:54, Oleksii Kurochko wrote: > --- a/xen/arch/riscv/pt.c > +++ b/xen/arch/riscv/pt.c > @@ -346,9 +346,33 @@ static int pt_mapping_level(unsigned long vfn, mfn_t mfn, unsigned long nr, > return level; > > /* > - * Don't take into account the MFN when removing mapping (i.e > - * MFN_INVALID) to calculate the correct target order. > + * `mfn` should be set properly in cases when modifying/destroying a > + * mapping to ensure the correct page table `level` is received. In the > + * case of `mfn` == INVALID_MFN, the `mask` will take into account only > + * `vfn` and could accidentally return an incorrect level. For example, > + * if `vfn` is page table level 1 aligned, but it was mapped as page table > + * level 0, then without the check below it will return `level` = 1 > + * because only `vfn`, which is page table level 1 aligned, is taken into > + * account when `mfn` == INVALID_MFN. > * > + * POPULATE shouldn't be considered as `va` hasn't been mapped yet. > + */ > + if ( mfn_eq(mfn, INVALID_MFN) && !(flags & PTE_POPULATE) ) > + { > + vaddr_t va = vfn << PAGE_SHIFT; > + paddr_t pa; > + unsigned long xen_virt_end = (XEN_VIRT_START + XEN_VIRT_SIZE - 1); > + > + if ( ((va >= DIRECTMAP_VIRT_START) && (va <= DIRECTMAP_VIRT_END)) || > + ((va >= XEN_VIRT_START) && (va <= xen_virt_end)) ) > + pa = virt_to_maddr(va); > + else > + pa = pt_walk(va); > + > + mfn = _mfn(paddr_to_pfn(pa)); > + } Doing a walk here and then another in pt_update() feels wasteful. I wonder whether the overall approach to page table updating doesn't want changing. It ought to be possible to tell an "update" operation to walk down to wherever the leaf entry is, and update there. Jan