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Mon, 25 Jan 2021 11:09:15 -0800 (PST) From: Oleksandr Tyshchenko To: xen-devel@lists.xenproject.org Cc: Oleksandr Tyshchenko , Stefano Stabellini , Julien Grall , Volodymyr Babchuk , Julien Grall Subject: [PATCH V5 22/22] xen/arm: Add mapcache invalidation handling Date: Mon, 25 Jan 2021 21:08:29 +0200 Message-Id: <1611601709-28361-23-git-send-email-olekstysh@gmail.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1611601709-28361-1-git-send-email-olekstysh@gmail.com> References: <1611601709-28361-1-git-send-email-olekstysh@gmail.com> X-ZohoMail-DKIM: pass (identity @gmail.com) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Oleksandr Tyshchenko We need to send mapcache invalidation request to qemu/demu everytime the page gets removed from a guest. At the moment, the Arm code doesn't explicitely remove the existing mapping before inserting the new mapping. Instead, this is done implicitely by __p2m_set_entry(). So we need to recognize a case when old entry is a RAM page *and* the new MFN is different in order to set the corresponding flag. The most suitable place to do this is p2m_free_entry(), there we can find the correct leaf type. The invalidation request will be sent in do_trap_hypercall() later on. Taking into the account the following the do_trap_hypercall() is the best place to send invalidation request: - The only way a guest can modify its P2M on Arm is via an hypercall - When sending the invalidation request, the vCPU will be blocked until all the IOREQ servers have acknowledged the invalidation Signed-off-by: Oleksandr Tyshchenko CC: Julien Grall Reviewed-by: Stefano Stabellini [On Arm only] Tested-by: Wei Chen --- Please note, this is a split/cleanup/hardening of Julien's PoC: "Add support for Guest IO forwarding to a device emulator" *** Please note, this patch depends on the following which is on review: https://patchwork.kernel.org/patch/11803383/ This patch is on par with x86 code (whether it is buggy or not). If there is a need to improve/harden something, this can be done on a follow-up. *** Changes V1 -> V2: - new patch, some changes were derived from (+ new explanation): xen/ioreq: Make x86's invalidate qemu mapcache handling common - put setting of the flag into __p2m_set_entry() - clarify the conditions when the flag should be set - use domain_has_ioreq_server() - update do_trap_hypercall() by adding local variable Changes V2 -> V3: - update patch description - move check to p2m_free_entry() - add a comment - use "curr" instead of "v" in do_trap_hypercall() Changes V3 -> V4: - update patch description - re-order check in p2m_free_entry() to call domain_has_ioreq_server() only if p2m->domain =3D=3D current->domain - add a comment in do_trap_hypercall() Changes V4 -> V5: - add Stefano's R-b - update comment in do_trap_hypercall() --- --- xen/arch/arm/p2m.c | 25 +++++++++++++++++-------- xen/arch/arm/traps.c | 20 +++++++++++++++++--- 2 files changed, 34 insertions(+), 11 deletions(-) diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index d41c4fa..26acb95d 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -1,6 +1,7 @@ #include #include #include +#include #include #include #include @@ -749,17 +750,25 @@ static void p2m_free_entry(struct p2m_domain *p2m, if ( !p2m_is_valid(entry) ) return; =20 - /* Nothing to do but updating the stats if the entry is a super-page. = */ - if ( p2m_is_superpage(entry, level) ) + if ( p2m_is_superpage(entry, level) || (level =3D=3D 3) ) { - p2m->stats.mappings[level]--; - return; - } +#ifdef CONFIG_IOREQ_SERVER + /* + * If this gets called (non-recursively) then either the entry + * was replaced by an entry with a different base (valid case) or + * the shattering of a superpage was failed (error case). + * So, at worst, the spurious mapcache invalidation might be sent. + */ + if ( (p2m->domain =3D=3D current->domain) && + domain_has_ioreq_server(p2m->domain) && + p2m_is_ram(entry.p2m.type) ) + p2m->domain->mapcache_invalidate =3D true; +#endif =20 - if ( level =3D=3D 3 ) - { p2m->stats.mappings[level]--; - p2m_put_l3_page(entry); + /* Nothing to do if the entry is a super-page. */ + if ( level =3D=3D 3 ) + p2m_put_l3_page(entry); return; } =20 diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c index 4cdd343..64b740b 100644 --- a/xen/arch/arm/traps.c +++ b/xen/arch/arm/traps.c @@ -1443,6 +1443,7 @@ static void do_trap_hypercall(struct cpu_user_regs *r= egs, register_t *nr, const union hsr hsr) { arm_hypercall_fn_t call =3D NULL; + struct vcpu *curr =3D current; =20 BUILD_BUG_ON(NR_hypercalls < ARRAY_SIZE(arm_hypercall_table) ); =20 @@ -1459,7 +1460,7 @@ static void do_trap_hypercall(struct cpu_user_regs *r= egs, register_t *nr, return; } =20 - current->hcall_preempted =3D false; + curr->hcall_preempted =3D false; =20 perfc_incra(hypercalls, *nr); call =3D arm_hypercall_table[*nr].fn; @@ -1472,7 +1473,7 @@ static void do_trap_hypercall(struct cpu_user_regs *r= egs, register_t *nr, HYPERCALL_RESULT_REG(regs) =3D call(HYPERCALL_ARGS(regs)); =20 #ifndef NDEBUG - if ( !current->hcall_preempted ) + if ( !curr->hcall_preempted ) { /* Deliberately corrupt parameter regs used by this hypercall. */ switch ( arm_hypercall_table[*nr].nr_args ) { @@ -1489,8 +1490,21 @@ static void do_trap_hypercall(struct cpu_user_regs *= regs, register_t *nr, #endif =20 /* Ensure the hypercall trap instruction is re-executed. */ - if ( current->hcall_preempted ) + if ( curr->hcall_preempted ) regs->pc -=3D 4; /* re-execute 'hvc #XEN_HYPERCALL_TAG' */ + +#ifdef CONFIG_IOREQ_SERVER + /* + * We call ioreq_signal_mapcache_invalidate from do_trap_hypercall() + * because the only way a guest can modify its P2M on Arm is via an + * hypercall. + * Note that sending the invalidation request causes the vCPU to block + * until all the IOREQ servers have acknowledged the invalidation. + */ + if ( unlikely(curr->domain->mapcache_invalidate) && + test_and_clear_bool(curr->domain->mapcache_invalidate) ) + ioreq_signal_mapcache_invalidate(); +#endif } =20 void arch_hypercall_tasklet_result(struct vcpu *v, long res) --=20 2.7.4