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[109.243.71.38]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b8037de004fsm1149128166b.45.2025.12.22.08.37.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Dec 2025 08:38:00 -0800 (PST) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 94ebe4c7-df54-11f0-9cce-f158ae23cfc8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1766421481; x=1767026281; darn=lists.xenproject.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=K1roM12Mw39RifSf3h2tzbDV94jY317E0NvXspPdXDM=; b=Ei+19PkuGnWiCN9JLPuSQ8p34702XDYS3jQI52OnQ1PO7GfWQHyjRyuAIYwGssel41 wfoW47wXkwzaNsTcsYZcZBpP4bbP5jNLF59Hwh0MRGrd7wns2TFNSLHBmo0xyE2h2NXk vpvzO/aEcePXtKAGK+bVt3v6unWr5/Cl5eZAX0HTG+aPZh5+2u+mLHIybWmaNCU5fa/Y NNCJUKBTTuyj3frdMQ9NhsoDa43b3oSlLNwNZ54J/22WjXBoPU8g/MmpMd8F/m+5RboO JJSu4oeEYDl6WcHdvvkG5qN1GAotSOZzShQvCDCdPK4kbjPSq0z1eQBSsriDYGql+1jk mH2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1766421481; x=1767026281; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=K1roM12Mw39RifSf3h2tzbDV94jY317E0NvXspPdXDM=; b=uU7MklnY5E9zULx/nYmQ3lE7JXzF387x7PFSzqD+zEiq2rQTSqKIORbwqW7cL3aFYS Xg+fH4Q3Erm3IwneriVCVDm0l8B491RNib3LKXsBZEJWafV4I5Urqb4o3+a0F8Q4nF4t iicZIlpFqff1CBHJm2yI+u9up/D981mJb3suUMiGIGiKU8XodUiyljhZn0Tqy3ThDTrj XB5mJoetrEFP2AhzOi5O2U+GwKR96DIcz37mDkI2kjwWX50TSE7kAN+SBzS1RM2HQSbg /7eEoMI6dV7OfthPY/qLR8buB3qmBY32Jkm5pMe5+NNTNefBftgh522qBA6ck8T94dtk OZQg== X-Gm-Message-State: AOJu0YzoYs/aDammFe9UuGL9IgLMiYbHU0Okr+Jm81AhmlztzgINohBX x7HWxqQ2OD8l7pQ/YzQaW6JieyvKac3GBh5qR04ejjx/eYzJcTfw7tNAHZ+oIg== X-Gm-Gg: AY/fxX65zQaFgrgg2ZKcp239Iqu0OL4r4SdL5ij3Iemx5ANo5vyu4c+onGUDHNcPPbw yeifFESO9jhgzT5D4ibdZ1NsrshlUhmtHqpV9xylxIu2v1GvMN18Mf+WJqqobmHwmq2axdtt45Z dCmnwORkMM8ItQwtSOlK0y6H0QPzmoPgrTD2NejPsj6F8oRvkKs9NPzb1u1OaMp/GbHZrbXxGAJ /5ZoktuTC2s/tdDGLl6KW/C4KLDqkTK19yAU1vznbQq0PEaKLAIQ7oD2O5eTQjVnIKZ3kqWSCb/ xcYCNQSwcbGyrcCQIV7TPYKRVeK4ITddiJ9cPQMAWxaHA2TRv9CrqcDRrRe6lILMS2Nn1/H3FuN pkwb8AuH7oPfll4lW5Xf1grt6QyXWjHlpp0SCfzb9cyOaAdrxbAjQDRp7zj9Nwg9Gh8EgwJngcm cD391JpB0Evb8ak6NWC2brfSuCNQ4Eu2cfhv31XVNRcnKzSEGcKlNAGGQ= X-Google-Smtp-Source: AGHT+IEtMrSq3gUuUEY2z045LwPXlSjaMt9lt7KSp0MWAxGMXSryGzCzI3aKm15gi35ZNFwbXJ4o9A== X-Received: by 2002:a17:907:1caa:b0:b77:1b03:66a1 with SMTP id a640c23a62f3a-b80371756c1mr1329058666b.41.1766421480634; Mon, 22 Dec 2025 08:38:00 -0800 (PST) From: Oleksii Kurochko To: xen-devel@lists.xenproject.org Cc: Oleksii Kurochko , Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , Jan Beulich , Julien Grall , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Stefano Stabellini Subject: [PATCH v8 1/3] xen/riscv: add support of page lookup by GFN Date: Mon, 22 Dec 2025 17:37:47 +0100 Message-ID: <5d10efb00eebb35861135280dfee391d0c55cf0d.1766406895.git.oleksii.kurochko@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @gmail.com) X-ZM-MESSAGEID: 1766421505659158500 Content-Type: text/plain; charset="utf-8" Introduce helper functions for safely querying the P2M (physical-to-machine) mapping: - add p2m_read_lock(), p2m_read_unlock(), and p2m_is_locked() for managing P2M lock state. - Implement p2m_get_entry() to retrieve mapping details for a given GFN, including MFN, page order, and validity. - Introduce p2m_get_page_from_gfn() to convert a GFN into a page_info pointer, acquiring a reference to the page if valid. - Introduce get_page(). Implementations are based on Arm's functions with some minor modifications: - p2m_get_entry(): - Reverse traversal of page tables, as RISC-V uses the opposite level numbering compared to Arm. - Removed the return of p2m_access_t from p2m_get_entry() since mem_access_settings is not introduced for RISC-V. - Updated BUILD_BUG_ON() to check using the level 0 mask, which correspon= ds to Arm's THIRD_MASK. - Replaced open-coded bit shifts with the BIT() macro. Signed-off-by: Oleksii Kurochko --- Changes in V8: - Drop the local variable masked_gfn inside check_outside_boundary() and fo= ld the is_lower conditionals into the for loop. - Initialize the local variable level in p2m_get_entry() to the root level and drop the explicit assignment when root page table wasn't found, as it now defaults to the root level. - Introduce gfn_limit_bits and use it to calculate the maximum GFN for the MMU second stage, and return the appropriate page_order when the GFN exce= eds this limit. --- Changes in V7: - Refactor check_outside_boundary(). - Reword the comment above p2m_get_entry(). - As at the moment p2m_get_entry() doesn't pass `t` as NULL we could drop "if ( t )" checks inside it to not have dead code now. - Add the check inside p2m_get_entry() that requested gfn is correct. - Add "if ( t )" check inside p2m_get_page_from_gfn() as it is going to be some callers with t =3D NULL. --- Changes in V6: - Move if-condition with initialization up in p2m_get_page_from_gfn(). - Pass p2mt to the call of p2m_get_entry() inside p2m_get_page_from_gfn() to avoid an issue when 't' is passed NULL. With p2mt passed to p2m_get_e= ntry() we will recieve a proper type and so the rest of the function will able = to continue use a proper type. - In check_outside_boundary() in the case when is_lower =3D=3D true fill th= e bottom bits of masked_gfn with all 1s. - Update code of check_outside_boundary() to return proper level in the cas= e when `level` is equal to 0. - Add ASSERT(p2m) in check_outside_boundary() to be sure that p2m isn't NUL= L as P2M_LEVEL_MASK() depends on p2m value. --- Changes in V5: - Use introduced in earlier patches P2M_DECLARE_OFFSETS() instead of DECLARE_OFFSETS(). - Drop blank line before check_outside_boundary(). - Use more readable version of if statements inside check_outside_boundary= (). - Accumulate mask in check_outside_boundary() instead of re-writing it for each page table level to have correct gfns for comparison. - Set argument `t` of p2m_get_entry() to p2m_invalid by default. - Drop checking of (rc =3D=3D P2M_TABLE_MAP_NOMEM ) when p2m_next_level(..= .,false,...) is called. - Add ASSERT(mfn & (BIT(P2M_LEVEL_ORDER(level), UL) - 1)); in p2m_get_entr= y() to be sure that recieved `mfn` has cleared lowest bits. - Drop `valid` argument from p2m_get_entry(), it is not needed anymore. - Drop p2m_lookup(), use p2m_get_entry() explicitly inside p2m_get_page_fr= om_gfn(). - Update the commit message. --- Changes in V4: - Update prototype of p2m_is_locked() to return bool and accept pointer-to= -const. - Correct the comment above p2m_get_entry(). - Drop the check "BUILD_BUG_ON(XEN_PT_LEVEL_MAP_MASK(0) !=3D PAGE_MASK);" = inside p2m_get_entry() as it is stale and it was needed to sure that 4k page(s)= are used on L3 (in Arm terms) what is true for RISC-V. (if not special exten= sion are used). It was another reason for Arm to have it (and I copied it to = RISC-V), but it isn't true for RISC-V. (some details could be found in response t= o the patch). - Style fixes. - Add explanatory comment what the loop inside "gfn is higher then the hig= hest p2m mapping" does. Move this loop to separate function check_outside_bou= ndary() to cover both boundaries (lower_mapped_gfn and max_mapped_gfn). - There is not need to allocate a page table as it is expected that p2m_get_entry() normally would be called after a corresponding p2m_set_e= ntry() was called. So change 'true' to 'false' in a page table walking loop ins= ide p2m_get_entry(). - Correct handling of p2m_is_foreign case inside p2m_get_page_from_gfn(). - Introduce and use P2M_LEVEL_MASK instead of XEN_PT_LEVEL_MASK as it isn'= t take into account two extra bits for root table in case of P2M. - Drop stale item from "change in v3" - Add is_p2m_foreign() macro and con= nected stuff. - Add p2m_read_(un)lock(). --- Changes in V3: - Change struct domain *d argument of p2m_get_page_from_gfn() to struct p2m_domain. - Update the comment above p2m_get_entry(). - s/_t/p2mt for local variable in p2m_get_entry(). - Drop local variable addr in p2m_get_entry() and use gfn_to_gaddr(gfn) to define offsets array. - Code style fixes. - Update a check of rc code from p2m_next_level() in p2m_get_entry() and drop "else" case. - Do not call p2m_get_type() if p2m_get_entry()'s t argument is NULL. - Use struct p2m_domain instead of struct domain for p2m_lookup() and p2m_get_page_from_gfn(). - Move defintion of get_page() from "xen/riscv: implement mfn_valid() and = page reference, ownership handling helpers" --- Changes in V2: - New patch. --- xen/arch/riscv/include/asm/p2m.h | 21 ++++ xen/arch/riscv/mm.c | 13 +++ xen/arch/riscv/p2m.c | 185 +++++++++++++++++++++++++++++++ 3 files changed, 219 insertions(+) diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/= p2m.h index b48693a2b41c..f63b5dec99b1 100644 --- a/xen/arch/riscv/include/asm/p2m.h +++ b/xen/arch/riscv/include/asm/p2m.h @@ -41,6 +41,9 @@ =20 #define P2M_GFN_LEVEL_SHIFT(lvl) (P2M_LEVEL_ORDER(lvl) + PAGE_SHIFT) =20 +#define P2M_LEVEL_MASK(p2m, lvl) \ + (P2M_TABLE_OFFSET(p2m, lvl) << P2M_GFN_LEVEL_SHIFT(lvl)) + #define paddr_bits PADDR_BITS =20 /* Get host p2m table */ @@ -234,6 +237,24 @@ static inline bool p2m_is_write_locked(struct p2m_doma= in *p2m) =20 unsigned long construct_hgatp(const struct p2m_domain *p2m, uint16_t vmid); =20 +static inline void p2m_read_lock(struct p2m_domain *p2m) +{ + read_lock(&p2m->lock); +} + +static inline void p2m_read_unlock(struct p2m_domain *p2m) +{ + read_unlock(&p2m->lock); +} + +static inline bool p2m_is_locked(const struct p2m_domain *p2m) +{ + return rw_is_locked(&p2m->lock); +} + +struct page_info *p2m_get_page_from_gfn(struct p2m_domain *p2m, gfn_t gfn, + p2m_type_t *t); + #endif /* ASM__RISCV__P2M_H */ =20 /* diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c index e25f995b727f..e9ce182d066c 100644 --- a/xen/arch/riscv/mm.c +++ b/xen/arch/riscv/mm.c @@ -673,3 +673,16 @@ struct domain *page_get_owner_and_reference(struct pag= e_info *page) =20 return owner; } + +bool get_page(struct page_info *page, const struct domain *domain) +{ + const struct domain *owner =3D page_get_owner_and_reference(page); + + if ( likely(owner =3D=3D domain) ) + return true; + + if ( owner !=3D NULL ) + put_page(page); + + return false; +} diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c index 8d572f838fc3..66943b969e8a 100644 --- a/xen/arch/riscv/p2m.c +++ b/xen/arch/riscv/p2m.c @@ -1057,3 +1057,188 @@ int map_regions_p2mt(struct domain *d, =20 return rc; } + +/* + * p2m_get_entry() should always return the correct order value, even if an + * entry is not present (i.e. the GFN is outside the range): + * [p2m->lowest_mapped_gfn, p2m->max_mapped_gfn] (1) + * + * This ensures that callers of p2m_get_entry() can determine what range of + * address space would be altered by a corresponding p2m_set_entry(). + * Also, it would help to avoid costly page walks for GFNs outside range (= 1). + * + * Therefore, this function returns true for GFNs outside range (1), and in + * that case the corresponding level is returned via the level_out argumen= t. + * Otherwise, it returns false and p2m_get_entry() performs a page walk to + * find the proper entry. + */ +static bool check_outside_boundary(const struct p2m_domain *p2m, gfn_t gfn, + gfn_t boundary, bool is_lower, + unsigned int *level_out) +{ + unsigned int level =3D P2M_ROOT_LEVEL(p2m); + bool ret =3D false; + + ASSERT(p2m); + + if ( is_lower ? gfn_x(gfn) < gfn_x(boundary) + : gfn_x(gfn) > gfn_x(boundary) ) + { + for ( ; level; level-- ) + { + unsigned long mask =3D BIT(P2M_GFN_LEVEL_SHIFT(level), UL) - 1; + + if ( is_lower ? (gfn_x(gfn) | mask) < gfn_x(boundary) + : (gfn_x(gfn) & ~mask) > gfn_x(boundary) ) + break; + } + + ret =3D true; + } + + if ( level_out ) + *level_out =3D level; + + return ret; +} + +/* + * Get the details of a given gfn. + * + * If the entry is present, the associated MFN, the p2m type of the mappin= g, + * and the page order of the mapping in the page table (i.e., it could be a + * superpage) will be returned. + * + * If the entry is not present, INVALID_MFN will be returned, page_order w= ill + * be set according to the order of the invalid range, and the type will be + * p2m_invalid. + */ +static mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn, + p2m_type_t *t, + unsigned int *page_order) +{ + unsigned int level =3D P2M_ROOT_LEVEL(p2m); + unsigned int gfn_limit_bits =3D + P2M_LEVEL_ORDER(level + 1) + P2M_ROOT_EXTRA_BITS(p2m, level); + pte_t entry, *table; + int rc; + mfn_t mfn =3D INVALID_MFN; + + P2M_BUILD_LEVEL_OFFSETS(p2m, offsets, gfn_to_gaddr(gfn)); + + ASSERT(p2m_is_locked(p2m)); + + *t =3D p2m_invalid; + + if ( gfn_x(gfn) > (BIT(gfn_limit_bits, UL) - 1) ) + { + if ( page_order ) + *page_order =3D gfn_limit_bits; + + return mfn; + } + + if ( check_outside_boundary(p2m, gfn, p2m->lowest_mapped_gfn, true, + &level) ) + goto out; + + if ( check_outside_boundary(p2m, gfn, p2m->max_mapped_gfn, false, &lev= el) ) + goto out; + + table =3D p2m_get_root_pointer(p2m, gfn); + + /* + * The table should always be non-NULL because the gfn is below + * p2m->max_mapped_gfn and the root table pages are always present. + */ + if ( !table ) + { + ASSERT_UNREACHABLE(); + goto out; + } + + for ( level =3D P2M_ROOT_LEVEL(p2m); level; level-- ) + { + rc =3D p2m_next_level(p2m, false, level, &table, offsets[level]); + if ( rc =3D=3D P2M_TABLE_MAP_NONE ) + goto out_unmap; + + if ( rc !=3D P2M_TABLE_NORMAL ) + break; + } + + entry =3D table[offsets[level]]; + + if ( pte_is_valid(entry) ) + { + *t =3D p2m_get_type(entry); + + mfn =3D pte_get_mfn(entry); + + ASSERT(!(mfn_x(mfn) & (BIT(P2M_LEVEL_ORDER(level), UL) - 1))); + + /* + * The entry may point to a superpage. Find the MFN associated + * to the GFN. + */ + mfn =3D mfn_add(mfn, + gfn_x(gfn) & (BIT(P2M_LEVEL_ORDER(level), UL) - 1)); + } + + out_unmap: + unmap_domain_page(table); + + out: + if ( page_order ) + *page_order =3D P2M_LEVEL_ORDER(level); + + return mfn; +} + +struct page_info *p2m_get_page_from_gfn(struct p2m_domain *p2m, gfn_t gfn, + p2m_type_t *t) +{ + struct page_info *page; + p2m_type_t p2mt; + mfn_t mfn; + + p2m_read_lock(p2m); + mfn =3D p2m_get_entry(p2m, gfn, &p2mt, NULL); + + if ( t ) + *t =3D p2mt; + + if ( !mfn_valid(mfn) ) + { + p2m_read_unlock(p2m); + return NULL; + } + + page =3D mfn_to_page(mfn); + + /* + * get_page won't work on foreign mapping because the page doesn't + * belong to the current domain. + */ + if ( unlikely(p2m_is_foreign(p2mt)) ) + { + const struct domain *fdom =3D page_get_owner_and_reference(page); + + p2m_read_unlock(p2m); + + if ( fdom ) + { + if ( likely(fdom !=3D p2m->domain) ) + return page; + + ASSERT_UNREACHABLE(); + put_page(page); + } + + return NULL; + } + + p2m_read_unlock(p2m); + + return get_page(page, p2m->domain) ? page : NULL; +} --=20 2.52.0