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Tue, 21 May 2024 08:16:59 -0700 (PDT) Message-ID: <245e535a-5b23-4d3e-83e5-dc797068652c@suse.com> Date: Tue, 21 May 2024 17:16:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] x86/mm: add API for marking only part of a MMIO page read only Content-Language: en-US To: =?UTF-8?Q?Marek_Marczykowski-G=C3=B3recki?= Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , xen-devel@lists.xenproject.org References: <2596964a55f710a300143aa5ae195566bacb4e00.1716260066.git-series.marmarek@invisiblethingslab.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: <2596964a55f710a300143aa5ae195566bacb4e00.1716260066.git-series.marmarek@invisiblethingslab.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 21.05.2024 04:54, Marek Marczykowski-Górecki wrote: > --- a/xen/arch/x86/include/asm/mm.h > +++ b/xen/arch/x86/include/asm/mm.h > @@ -522,9 +522,27 @@ extern struct rangeset *mmio_ro_ranges; > void memguard_guard_stack(void *p); > void memguard_unguard_stack(void *p); > > +/* > + * Add more precise r/o marking for a MMIO page. Range specified here > + * will still be R/O, but the rest of the page (not marked as R/O via another > + * call) will have writes passed through. > + * The start address and the size must be aligned to SUBPAGE_MMIO_RO_ALIGN. > + * > + * This API cannot be used for overlapping ranges, nor for pages already added > + * to mmio_ro_ranges separately. > + * > + * Return values: > + * - negative: error > + * - 0: success > + */ > +#define SUBPAGE_MMIO_RO_ALIGN 8 This isn't just alignment, but also (and perhaps more importantly) granularity. I think the name wants to express this. > @@ -4910,6 +4921,260 @@ long arch_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void) arg) > return rc; > } > > +/* > + * Mark part of the page as R/O. > + * Returns: > + * - 0 on success - first range in the page > + * - 1 on success - subsequent range in the page > + * - <0 on error > + * > + * This needs subpage_ro_lock already taken */ Nit: Comment style (full stop and */ on its own line). > +static int __init subpage_mmio_ro_add_page( > + mfn_t mfn, unsigned int offset_s, unsigned int offset_e) > +{ > + struct subpage_ro_range *entry = NULL, *iter; > + unsigned int i; > + > + list_for_each_entry(iter, &subpage_ro_ranges, list) > + { > + if ( mfn_eq(iter->mfn, mfn) ) > + { > + entry = iter; > + break; > + } > + } > + if ( !entry ) > + { > + /* iter == NULL marks it was a newly allocated entry */ > + iter = NULL; > + entry = xzalloc(struct subpage_ro_range); > + if ( !entry ) > + return -ENOMEM; > + entry->mfn = mfn; > + } > + > + for ( i = offset_s; i <= offset_e; i += SUBPAGE_MMIO_RO_ALIGN ) > + { > + int oldbit = __test_and_set_bit(i / SUBPAGE_MMIO_RO_ALIGN, > + entry->ro_qwords); Why int, not bool? > + ASSERT(!oldbit); > + } > + > + if ( !iter ) > + list_add(&entry->list, &subpage_ro_ranges); > + > + return iter ? 1 : 0; > +} > + > +/* This needs subpage_ro_lock already taken */ > +static void __init subpage_mmio_ro_remove_page( > + mfn_t mfn, > + int offset_s, > + int offset_e) Can either of these be negative? The more that ... > +{ > + struct subpage_ro_range *entry = NULL, *iter; > + unsigned int i; ... this is used ... > + list_for_each_entry(iter, &subpage_ro_ranges, list) > + { > + if ( mfn_eq(iter->mfn, mfn) ) > + { > + entry = iter; > + break; > + } > + } > + if ( !entry ) > + return; > + > + for ( i = offset_s; i <= offset_e; i += SUBPAGE_MMIO_RO_ALIGN ) ... with both of them? > + __clear_bit(i / SUBPAGE_MMIO_RO_ALIGN, entry->ro_qwords); > + > + if ( !bitmap_empty(entry->ro_qwords, PAGE_SIZE / SUBPAGE_MMIO_RO_ALIGN) ) > + return; > + > + list_del(&entry->list); > + if ( entry->mapped ) > + iounmap(entry->mapped); > + xfree(entry); > +} > + > +int __init subpage_mmio_ro_add( > + paddr_t start, > + size_t size) > +{ > + mfn_t mfn_start = maddr_to_mfn(start); > + paddr_t end = start + size - 1; > + mfn_t mfn_end = maddr_to_mfn(end); > + unsigned int offset_end = 0; > + int rc; > + bool subpage_start, subpage_end; > + > + ASSERT(IS_ALIGNED(start, SUBPAGE_MMIO_RO_ALIGN)); > + ASSERT(IS_ALIGNED(size, SUBPAGE_MMIO_RO_ALIGN)); > + if ( !IS_ALIGNED(size, SUBPAGE_MMIO_RO_ALIGN) ) > + size = ROUNDUP(size, SUBPAGE_MMIO_RO_ALIGN); > + > + if ( !size ) > + return 0; > + > + if ( mfn_eq(mfn_start, mfn_end) ) > + { > + /* Both starting and ending parts handled at once */ > + subpage_start = PAGE_OFFSET(start) || PAGE_OFFSET(end) != PAGE_SIZE - 1; > + subpage_end = false; > + } > + else > + { > + subpage_start = PAGE_OFFSET(start); > + subpage_end = PAGE_OFFSET(end) != PAGE_SIZE - 1; > + } > + > + spin_lock(&subpage_ro_lock); > + > + if ( subpage_start ) > + { > + offset_end = mfn_eq(mfn_start, mfn_end) ? > + PAGE_OFFSET(end) : > + (PAGE_SIZE - 1); > + rc = subpage_mmio_ro_add_page(mfn_start, > + PAGE_OFFSET(start), > + offset_end); > + if ( rc < 0 ) > + goto err_unlock; > + /* Check if not marking R/W part of a page intended to be fully R/O */ > + ASSERT(rc || !rangeset_contains_singleton(mmio_ro_ranges, > + mfn_x(mfn_start))); > + } > + > + if ( subpage_end ) > + { > + rc = subpage_mmio_ro_add_page(mfn_end, 0, PAGE_OFFSET(end)); > + if ( rc < 0 ) > + goto err_unlock_remove; > + /* Check if not marking R/W part of a page intended to be fully R/O */ > + ASSERT(rc || !rangeset_contains_singleton(mmio_ro_ranges, > + mfn_x(mfn_end))); > + } > + > + spin_unlock(&subpage_ro_lock); > + > + rc = rangeset_add_range(mmio_ro_ranges, mfn_x(mfn_start), mfn_x(mfn_end)); > + if ( rc ) > + goto err_remove; > + > + return 0; > + > + err_remove: > + spin_lock(&subpage_ro_lock); > + if ( subpage_end ) > + subpage_mmio_ro_remove_page(mfn_end, 0, PAGE_OFFSET(end)); > + err_unlock_remove: > + if ( subpage_start ) > + subpage_mmio_ro_remove_page(mfn_start, PAGE_OFFSET(start), offset_end); > + err_unlock: > + spin_unlock(&subpage_ro_lock); > + return rc; > +} > + > +static void __iomem *subpage_mmio_get_page(struct subpage_ro_range *entry) > +{ > + void __iomem *mapped_page; > + > + if ( entry->mapped ) > + return entry->mapped; > + > + mapped_page = ioremap(mfn_x(entry->mfn) << PAGE_SHIFT, PAGE_SIZE); mfn_to_maddr() or some such? > + spin_lock(&subpage_ro_lock); > + /* Re-check under the lock */ > + if ( entry->mapped ) > + { > + spin_unlock(&subpage_ro_lock); > + iounmap(mapped_page); What if ioremap() failed? Jan