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Mon, 15 Jul 2024 07:58:56 -0700 (PDT) Message-ID: <945afaf1-8223-4e3e-bf6d-98a6fad66f78@suse.com> Date: Mon, 15 Jul 2024 16:58:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 8/8] xen/riscv: introduce early_fdt_map() To: Oleksii Cc: Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Julien Grall , Stefano Stabellini , xen-devel@lists.xenproject.org References: <4e4f94817fb3bba5f52336ea0b4491f7bc867d49.1720799926.git.oleksii.kurochko@gmail.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 15.07.2024 15:58, Oleksii wrote: > On Mon, 2024-07-15 at 10:52 +0200, Jan Beulich wrote: >> On 12.07.2024 18:22, Oleksii Kurochko wrote: >>> +    rc = map_pages_to_xen(BOOT_FDT_VIRT_START, >>> maddr_to_mfn(base_paddr), >>> +                          SZ_2M >> PAGE_SHIFT, >>> +                          PAGE_HYPERVISOR_RO | _PAGE_BLOCK); >>> +    if ( rc ) >>> +        panic("Unable to map the device-tree.\n"); >>> + >>> +    offset = fdt_paddr % XEN_PT_LEVEL_SIZE(1); >>> +    fdt_virt = (void *)BOOT_FDT_VIRT_START + offset; >>> + >>> +    if ( fdt_magic(fdt_virt) != FDT_MAGIC ) >>> +        return NULL; >>> + >>> +    size = fdt_totalsize(fdt_virt); >>> +    if ( size > BOOT_FDT_VIRT_SIZE ) >>> +        return NULL; >>> + >>> +    if ( (offset + size) > SZ_2M ) >>> +    { >>> +        rc = map_pages_to_xen(BOOT_FDT_VIRT_START + SZ_2M, >>> +                              maddr_to_mfn(base_paddr + SZ_2M), >>> +                              SZ_2M >> PAGE_SHIFT, >>> +                              PAGE_HYPERVISOR_RO | _PAGE_BLOCK); >>> +        if ( rc ) >>> +            panic("Unable to map the device-tree\n"); >>> +    } >> >> Why this two part mapping? And why are you mapping perhaps much more >> than "size"? > I wasn't able to find if RISC-V has a requirement for alignment of FDT > address so I decided to follow Arm where FDT is required to be placed > on a 8-byte boundary, so FDT can cross a 2MB boundary, so the second > 2MB page should be mapped if the FDT is crossing the 2MB boundary. This explains why you may need to map more than 2Mb (which wasn't the question), but it doesn't explain why you need to do it in two steps. Jan