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Mon, 17 Nov 2025 23:12:09 -0800 (PST) Message-ID: <0ff1d79b-a7c2-4fc0-a335-17cbdb977dfc@suse.com> Date: Tue, 18 Nov 2025 08:12:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 27/28] xen/domctl: make HVM_PARAM_IDENT_PT conditional upon CONFIG_MGMT_HYPERCALLS To: "Penny, Zheng" Cc: "Huang, Ray" , "oleksii.kurochko@gmail.com" , Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , "xen-devel@lists.xenproject.org" References: <20251013101540.3502842-1-Penny.Zheng@amd.com> <20251013101540.3502842-28-Penny.Zheng@amd.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 18.11.2025 07:45, Penny, Zheng wrote: > [Public] > >> -----Original Message----- >> From: Jan Beulich >> Sent: Thursday, October 30, 2025 9:35 PM >> To: Penny, Zheng >> Cc: Huang, Ray ; oleksii.kurochko@gmail.com; Andrew >> Cooper ; Roger Pau Monné ; >> xen-devel@lists.xenproject.org >> Subject: Re: [PATCH v3 27/28] xen/domctl: make HVM_PARAM_IDENT_PT >> conditional upon CONFIG_MGMT_HYPERCALLS >> >> On 13.10.2025 12:15, Penny Zheng wrote: >>> Helper domctl_lock_{acquire,release} is domctl_lock, which >>> HVM_PARAM_IDENT_PT uses to ensure synchronization and hence being a >> toolstack-only operation. >>> So we shall make HVM_PARAM_IDENT_PT conditional upon >>> CONFIG_MGMT_HYPERCALLS, returning -EOPNOTSUPP when >> MGMT_HYPERCALLS=n. >>> >>> Suggested-by: Jan Beulich >> >> I fear this isn't quite what I suggested. The param get/set are XSM_TARGET, i.e. >> can be used by DM as well. The particular one here shouldn't be used by a DM, but >> that's a different question. Similarly in principle the PVH Dom0 building code should >> be able to use this path; it doesn't right now in favor of some open- coding. >> >> What iirc I did suggest was that the serialization isn't needed when no domctl can >> be used to otherwise alter (relevant) guest state. > > Ah, true, serialization isn't needed when MGMT_HYPERCALLS=n, as no domctl-op could alter the guest state at the same time. > Then maybe adding IS_ENABLED() checking is enough: Yes, that or indeed introducing stubs. Which one is the lesser evil I'm having a hard time determining. Hence I'd suggest that you go with the below, unless someone else chimes in. Jan > ``` > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c > index 5a50721bd0..4e1b3ee5f4 100644 > --- a/xen/arch/x86/hvm/hvm.c > +++ b/xen/arch/x86/hvm/hvm.c > @@ -4324,7 +4324,7 @@ static int hvm_set_param(struct domain *d, uint32_t index, uint64_t value) > * the domctl_lock. > */ > rc = -ERESTART; > - if ( !domctl_lock_acquire() ) > + if ( IS_ENABLED(CONFIG_MGMT_HYPERCALLS) && !domctl_lock_acquire() ) > break; > > rc = 0; > @@ -4334,7 +4334,8 @@ static int hvm_set_param(struct domain *d, uint32_t index, uint64_t value) > paging_update_cr3(v, false); > domain_unpause(d); > > - domctl_lock_release(); > + if ( IS_ENABLED(CONFIG_MGMT_HYPERCALLS) ) > + domctl_lock_release(); > break; > case HVM_PARAM_DM_DOMAIN: > /* The only value this should ever be set to is DOMID_SELF */ > ``` > >> >> Jan